1. Field of the Invention
This invention relates to magneto-optical disc apparatus utilizing the Kerr effect or the Faraday effect, for example, and is more particularly concerned with reproducing apparatus employing an improved head that includes a fixed head portion and a movable head portion.
2. Description of the Prior Art
In Japanese Laid-Open Patent Application No. 52444/1984 a reproducing head of a recording-reproducing apparatus of the magneto-optical disc type (hereinafter referred to generally as a "disc") is proposed, in which the head has a movable portion and a fixed portion. The movable head portion has a control system comprising an objective lens movable radially of the disc, a mirror, a focusing system, a tracking system, and a light source unit. The fixed head portion has an analyzer for receiving light reflected from the disc, an imaging optical system, and a photoelectric converting element. Transmission of signals between the two head portions is effected by parallel light beams.
The apparatus of the aforesaid Japanese patent application is advantageous in that the movable head portion is simple and lightweight and in that the apparatus is compact, provides improved efficiency of utilization of the light, and permits high-speed access. However, these advantages are offset somewhat by the need for providing a high accuracy slider mechanism for the movable head portion, which tends to increase the bulkiness and the cost of the apparatus. Such a slider mechanism is required because when the movable head portion moves radially of the disc, movements other than radial movement cause the plane of polarization of the light entering the analyzer to rotate undesirably, resulting in an error in the reproduction of the information recorded on the disc.